Before I insert a longer bolt and hammer on it like some kind of roofer, can anyone confirm this is a wedge-type ECC and that I'd be doing the right thing to hammer at it?

From searches and other sites, I'm 90% sure I'm okay, but would prefer a little support first. It's the stock eccentric on this 2004 Trek T-2000. By the way, is there a special tool to remove the small aluminum 'lock nut' or whatever it's called? The notches are too far apart even for my largest screw driver.

If you plan to pull the eccentric and lube it all to prevent corrosion or minimize this problem next time, get those cranks off while it's still tight.

Not sure what to say in regards to the jamb nut being wider than your screwdriver. I guess buy a larger screwdriver or maybe locate a huge setscrew that uses an Allen wrench. The proper tool though is possibly a chainring bolt tool, most times very inexpensive.

My true thoughts are that the jamb nut is not truly a jamb nut but rather a seat for when the bolt is loosened. This will allow the bolt head to seat and then begin pushing the expander loose.

Before you beat it apart, did you try inserting the Allen wrench through the jamb nut and then loosen it? Once the bolt is loosened, it will get easy to turn for a few revs, then get difficult again as it unseats the wedge.

NO, do not hammmer on this. You have a self extracting eccentric and a hammer is not ever needed. What you do is leave the "locknut" in, put the allen wrench throught the locknut and start loosening the wedge bolt. Continue to loosen the wedge bolt until the head of the wedge bolt hits against the locknut. Keep loosening the wedge bolt for several more turns and the wedge will be driven out the other side. It's a great design but many don't know how to use it. Even the bike shop where I bought my tandem didn't know how to use it.

Cool! Thanks guys. I see that hammering may have worked, but using that nut (maybe I should call it a "stop nut") is definitely a much more elegant way to do it. I didn't think of that at all. I'll try it out this evening.

I'll track down a chainring bolt tool also. Since that nut is aluminum, it bothers me to be using that screw driver.

ct-vt-trekke has it 100% right, it is a self extracting eccentric.
So, since you have both the ""stop nut"" and the allen-head bolt out of the eccentric at the moment, first put the allen bolt back in the eccentric until it lightly seats,, then put back the "stop nut just like it was, then put an allen wrench through the 'stop nut' and turn the allen bolt counter clockwise....it will turn easy for a turn or two, then it will get harder to turn as it butts against the backside of the 'stop nut' for a turn or two until it pushes the wedge piece free on the opposite side of the eccentric.
It is a nice simple setup that works well. Good luck